/Engine/Source/Runtime/Experimental/Animation/Constraints/Public/TransformConstraint.h
Manages changes on the child/parent transformable handle. This can be used to update internal data (i.e. offset) when transform changes outside of that system and need to trigger changes within the constraint itself.
virtual void OnHandleModified ( [UTransformableHandle](API\Runtime\Constraints\UTransformableHandle) * InHandle, EHandleEvent InEvent )